In the case of the arc-light the circuit is open (that is, broken), technically speaking, but the current is still flowing.
Anyway, look the man over when he passes under the arc-light.
Even the arc-light that Foucault produced in 1844 was not utilized then.
His face was well lighted by the arc-light under the arch of the door.
Under the blue white of the arc-light, her face was that of a dead woman.
They were under the arc-light that flooded the entrance to the park.
The arc-light outside had gone out and dawn was approaching.
This leaves the (electric) arc-light as the only one which is really available.
Tom was under the arc-light at the gates when the volunteers straggled out.
The gas has been condensed to a colourless liquid, and frozen to an opaque solid which glows like a minute arc-light.